JPS63111602A - High performance rare earth cast magnet - Google Patents

Abstract

PURPOSE:To provide characteristic of a rare earth cast magnet having those better than those of an Alnico magnet only by a casting method without necessity of a special cooling facility by limiting the composition of an R-Fe-B magnet and limiting the types and the quantities of additives. CONSTITUTION:A rare earth-iron boron permanent magnet is cast with a material represented by a composition formula of RX(FeaCO1-a)1-X-Y-ZMyBz. Thus, the permanent magnet can be manufactured without necessity of separate steps divided to many stages of so-called powder metallurgical method, without requirement of a high speed quenching unit and without limit of the shape of a ribbon or the like. Where R in the formula is one or more rare earth elements including Y, M is at least one element selected from a group consisting of Al, Ni, Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta, W and Cu, x, y, z, a are atomic ratios, and 0.03<=x<=0.25; 0.005<=y<=0.15; 0.02<=z<=0.15; 0.5<=a<=1.0.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to rare earth-iron-boron permanent magnets (hereinafter referred to as R-F
e-B series magnets), and in more detail, R-Fe- which achieved high performance through casting.
This relates to B-based magnets.

[Conventional technology]

R-Fe-B magnets achieve excellent magnetic properties by not using expensive cobalt or the like as an essential component and by using a large amount of iron, which is an inexpensive industrial material. Up until now, efforts have been made to further improve magnetic properties, achieve good magnetic properties while using cheaper elements, or improve workability, thereby reducing the amount of rare earth cobalt that is conventionally used in general permanent magnets. Research is being actively conducted to provide R--Fe--B magnets that can replace or compete with permanent magnets and ferrite magnets.

Various manufacturing methods have been proposed for R-Fe-B magnets, but they can be broadly classified into the following two types. One method uses a high-speed quenching method published in Japanese Patent Application Laid-Open No. 59-64739. In this method, molten alloy is injected onto a copper or iron roll rotating at high speed.
A very fast cooling rate of 5°C/sec or more is obtained, and an alloy in an amorphous state or a mixed state of amorphous and crystalline materials is obtained. In this case, a high coercive force can be obtained by selecting an appropriate cooling rate. Furthermore, high coercive force can be obtained by rapidly cooling at a higher speed and performing appropriate heat treatment. The shape of the obtained alloy is ribbon-like and magnetically isotropic. In order to use this isotropic ribbon-shaped alloy as a permanent magnet, the ribbon is crushed, mixed with resin, and molded to form a resin magnet, or it is densified by hot pressing to form a scale block magnet. According to GM's publication in Japanese Patent Laid-Open No. 60-100402, it is said that the block can be made anisotropic by a construction method called die ampscent.

The second method is the powder metallurgy sintering method announced in Japanese Patent Application Laid-Open No. 59-46008. The obtained alloy ingot is crushed, molded, sintered,
A permanent magnet is obtained by performing an aging process. Since molding is performed while applying a magnetic field, an anisotropic magnet can be obtained.

The process in which coercive force is imparted to the alloy in this method is a sintering process, and the magnetic properties in the ingot manufacturing process do not exhibit properties as a magnet.

[Problem that the invention seeks to solve]

As mentioned above, R-Fe-B magnets have conventionally been manufactured by either a high-speed quenching method or a powder metallurgy sintering method. Although well-known alnico magnets are manufactured by a casting method, there has been no known method for manufacturing R-Fe-B magnets by a casting method and imparting high performance. For this reason, it is not possible to sufficiently meet the demands of customers, which can be easily met by the casting method, and there are also problems such as requiring equipment such as high-speed quenching equipment and a press, resulting in a long process.

As is well known, alnico magnets are Fe-Al-Ni-C
It consists of o and additives, and is given magnetic properties by casting a molten alloy. In some cases, the cast body may be further heat treated to improve its properties, but the basic magnetic properties are maintained after casting. The inventors have discovered that R
Research was conducted with the aim of providing -Fe-B magnets that, like alnico magnets, have basic magnetic properties after casting.

In addition, the alnico magnet is isotropic and has a value of 2.5 MGOe.
Even the anisotropic one has an energy product of only 10 MGOe, and the coercive force has a low value of less than 1.5 KO. Therefore, unless the magnetic properties of cast R-Fe-B magnets exceed those of alnico, there is no superiority in terms of magnetic properties. However, conventionally, R-Fe-B magnets comparable to alnico magnets have not been obtained by casting methods. In other words, magnetic properties could not be obtained without ultra-high-speed cooling.

Means for Solving Problem C] The present inventors have discovered that the casting method can be applied by limiting the composition of the R-Fe-B magnet and limiting the type and amount of additives.

Based on this knowledge, the present invention provides R(FeaCo+-
m), -, -, MyB, (where R is one or more rare earth elements including Y, M is Al, Ni, Ti
, V, Cr.

Mn, Zr, Nb, Mo, Hf,
At least one element selected from the group consisting of Ta, w, Cu, X, y, 2 are atomic ratios, 0.0
3≦x≦0.25; 0.005≦y≦0.15; 0
．． The present invention provides a high-performance rare earth cast magnet characterized by being represented by the following compositional formula: 02≦z≦0.15; 0.5≦a≦1.

Although the above composition partially overlaps with the composition of conventionally published R-Fe-B magnets, it is characterized within the above composition range. That is, it has been found that when these additive elements are added, grain growth during the cooling process from the molten metal is suppressed compared to alloys without additives, and as a result, high coercive force can be obtained. Among these additive elements, Nb and Zr are particularly effective. When such additive elements are added, high-speed casting to produce blocks at a speed lower than the 105° C./sec or higher used in the high-speed quenching method is also preferable from the viewpoint of coercive force iHc. By using the casting method, permanent magnets can be manufactured without the need for complex, high-speed quenching equipment, no restrictions on the shape of ribbons, etc., and without the need for the multiple steps of the so-called powder metallurgy process. It became so. x, y in the above composition formula
, z is the first thing that can be provided. Next, X in the above compositional formula.

The reason for the limitation from the viewpoint of magnetic properties of y and z will be explained.

When X (rare earth element content) is less than 0.03, the coercive force decreases, while when X is greater than 0.25, the residual magnetic flux density (Br) decreases. y (M element-Aβ.

Ni, Ti, V, Cr, Mn, Zr
, Nb + Mo + Hf , Ta , W, Cu) is 0.
When y is smaller than 005, high coercive force cannot be obtained, and when y is larger than 0.15, the residual magnetic flux density (Br) decreases. If 2 (boron content) is less than 0.02, the coercive force will decrease, while if 2 is greater than 0.15, the residual magnetic flux density (Br) will decrease. In this way, when x, y, and z are outside the predetermined range and the coercive force or residual magnetic flux density (Br) decreases, the magnetic properties of the R-Fe-B field magnet will change depending on the conventional high-speed quenching method or powder metallurgy sintering method. In addition to being significantly inferior to the magnetic properties of the magnet obtained by the method, it is also lower than the maximum energy product of the alnico magnet. On the other hand, x+ V +
2 is within a predetermined range, the magnetic properties of the R-Fe-B field magnet in the cast state will be 14MGOe, which has been announced to be obtained by the conventional high-speed quenching method or the powder metallurgy sintering method, respectively.
Although it does not reach the highest value of maximum energy product of 45MGOe, it completely satisfies the magnetic properties required of permanent magnets for various uses.

In the above composition of the R-Fe-B field magnet of the present invention, Fe
is replaced with Co (cobalt), and Fe/Kasatei (Fe+Co
)≧0.5, the temperature characteristics of residual magnetic flux density are improved. If the amount of Co substitution exceeds 50 atomic %, the residual magnetic flux density will decrease, which is not preferable.

The method for manufacturing the R-Fe-B field magnet according to the present invention will be described below, but the magnet of the present invention can be manufactured by any casting method, not limited to the method described below.

An appropriate amount is selected from a raw material group consisting of rare earth metals, iron, boron (or ferroboron), and transition metals, melted in a non-oxidizing atmosphere, alloyed, and then continuously cast into a mold.
Obtain ingot. The mold may be any type such as a metal mold, sand mold, shell mold, lost wax, or the like. The size of the ingot can be arbitrary, and parts for automobiles, computers, and motors in which high-performance magnets are used can be manufactured from the ingot.

300°C to 900°C to further improve the performance of ingot magnets
It is also possible to choose to add, as appropriate, a step of performing heat treatment at a temperature of , a step of applying a magnetic field during the heat treatment, and a step of processing into a product shape.

Of course, the obtained magnet can be used as is, but
- It is also possible to make a resin magnet by first pulverizing it to an appropriate particle size, mixing it with a resin, and molding it. In some cases, in order to achieve anisotropy, the ingot is crushed, molded in a magnetic field, and sintered.
It is also possible to carry out a statute of limitations.

〔Effect of the invention〕

An effect like this is achieved.

(1) Achievement of low 02 - In particular, with powder metallurgy sintering of 5 g, there are many steps to treat the powder, and the powder compact is heated at high temperature, so oxidation of rare earth components in the powder occurs frequently. For this reason, the amount of rare earth components in the powder must be increased in anticipation of oxidation.

However, according to the present invention, the basic magnetic properties of an R-Fe-B field magnet are achieved only through the steps of alloying and casting, so the oxidation of the rare earth components in the powder is reduced (approximately 110
00pp or less). Therefore, deterioration of magnetic properties due to oxidation is reduced, and there is no need to add a large amount of rare earth components in advance. Furthermore, when comparing the original method and the powder metallurgy method with the same composition, the original method yields a higher residual magnetic flux density.

(2) Improved yield - Compared to the powder metallurgy sintering method, the number of steps is reduced, which improves the yield.

Furthermore, since sintered bodies tend to warp and crack, large machining allowances are required to make them into product shapes.However, with the present invention, only a small amount of machining is required as long as the mold can be designed into a shape. do not have.

(3) Arbitrariness of shape - The design of the mold is based on the powder molding mold,
It is more flexible than hot press mold designs and can accommodate a wide range of product shape requirements. Furthermore, the shape of the magnet material (product) is not limited to one type, unlike the high-speed quenching method for obtaining a ribbon shape.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

〔Example〕

An alloy whose composition is shown in Table 1 was melted in a high frequency melting furnace and cast into a mold. The dimensions of the obtained ingots were as follows: As can be seen by comparing the comparative example in Table 1 with the inventive example, the magnetic properties after casting are significantly different due to compositional limitations.

Margin below

Claims (1)

[Claims] 1. R_x(Fe_aCo_1_-_a)_1_-_x
＿−＿y＿−＿zM_yB_z (However, R is one or more rare earth elements including Y, M is Al, Ni, Ti, V, C
r, Mn, Zr, Nb, Mo, Hf, Ta, W, at least one element selected from the group consisting of Cu, x, y
, z, a are atomic ratios, 0.03≦x≦0.25;0
．． 005≦y≦0.15;0.02≦z≦0.15;0
．． A high-performance rare earth cast magnet characterized by being represented by the composition formula: 5≦a≦1.0. 2. The high-performance rare earth cast magnet according to claim 1, wherein M is one of Zr and Nb.